The invention relates to an energy supply device which comprises a fan wheel generator for a mortar fuse, e.g., for rotating a component of a mortar fuse, e.g., a detonator-carrying body or a battery charger. The generator includes a shaft which can be driven at high speed by a fan wheel. The shaft is rotatably supported in a housing body of the energy supply device.
In the case of mortar fuses or mortar fuse systems with integrated electrical functions, fan wheel generators are usually employed to provide the supply of energy. The nominal or operating rotary speed of fan wheel generators of that kind is very high, being for example 100,000 rpm. That nominal or operating speed has to be guaranteed during an operating period of the order of magnitude of 3 minutes. Hitherto the fan wheel shaft which rotates at high speed has been supported by high-speed ball bearings. The procurement price of such high-speed ball bearings is very high. Two such high-speed ball bearings are required to support the fan wheel shaft. This means that known energy supply devices of the above-indicated kind involve relatively high production costs.
It is known from U.S. Pat. No. 3,808,972 to make a bearing for an oscillating fan shaft of a bomb completely out of polytetrafluoroethylene (PTFE). However, there occurs the disadvantage that frictional heat is stored or builds up the relatively thick layer of PTFE. Consequently, the PTFE becomes brittle and loses its lubricating function. The shaft will then freeze, i.e., lock-up.
An object of the present invention is to provide an energy supply device of the kind set forth in the opening part of this specification, wherein the shaft is properly lubricated for the expected travel time, without experiencing overheating.
Another object is to provide such a device, the production costs of which are comparatively low, while at the same time resistance to heat is enhanced.